CCA is used to determine a busy/idle state of a channel, that is, whether the channel is already occupied by another device, and if yes, wait for a period of time before the process is performed again, or if not, the channel is used to transmit data. A conflict on a radio channel can be effectively prevented by means of CCA.
In a multi-carrier application scenario, due to a limitation of a capability of an actual device, after user equipment successfully completes CCA on a carrier and starts to transmit data, local leakage of a transmitted signal results in that a signal from the device is also received on a neighboring carrier of the carrier. When performing CCA on the neighboring carrier of the used carrier, the user equipment may mistakenly consider that the interference is from a signal that is transmitted by another user equipment on the carrier, and draws a wrong conclusion of a busy state. As a result, the device gives up access attempts on the carrier that is interfered with, leading to a waste of channel resources and producing the problem of CCA blocking between carriers.